Essential oils like lemongrass, oregano, rosemary, white thyme, and tea tree are great antimicrobial agents. Don't be afraid to combine some together to make treatments more effective. Oils such as olive, almond, castor that some like to use on their hair are carrier oils so they are different. These oils might not clog pores on a healthy scalp but be cautious using carrier oils on an unhealthy scalp because it might do more harm than good.
Although all of our conditions might look similar, I'm confident we all have different strains of microbes causing this condition. Therefore, that's why some treatments work for others while doing little or nothing for someone else. Don't get discouraged and keep trying different ideas until you find some relief.